1. Field of the Invention
This invention relates to a magnetic puffer type gas circuit breaker in which an electromagnetic force produced in an electromagnetic driving unit by a current to be interrupted is employed as a breaking energizing force. More specifically, it relates to improvements in the relationship and arrangement between an electromagnetic coil and an electromagnetic repulsive member constituting the electromagnetic driving unit.
2. Description of the Prior Art
The puffer type gas circuit breaker has advantages in that the structure is simple and, since the pressure of SF.sub.6 gas used as an insulating medium may be low, the SF.sub.6 gas does not liquidize. However, it has the disadvantage that due to provision of a puffer unit for compressing the SF.sub.6 gas and blowing it against arcs produced between the contacts, a very large operating force is required for the interruption of a current which exceeds 50 kA, for example. With recent increases in the demand for electric power, there is the tendency to increase the current level at which circuit breakers are to be operated. For this reason, the required operating force for operating the puffer type circuit breaker increases more and more. In order to cope with this problem, the so-called magnetic puffer type gas circuit breaker has been developed in which an electromagnetic force is produced in an electromagnetic driving unit by the current to be interrupted as it flows through the circuit breaker and in which the electromagnetic force is utilized as a supplemental operating force of the circuit breaker.
A prior art magnetic puffer type gas circuit breaker, however, has the disadvantage that when arcs are produced between contacts as a result of an initial discharge during the closing operation of the circuit breaker, a current flows through the electromagnetic coil of the electromagnetic driving unit, an electromagnetic force is produced in the electromagnetic driving unit and this electromagnetic force acts to impede the closing operation.